Lotus japonicus symRK-14 uncouples the cortical and epidermal symbiotic program

SYMRK is a leucine-rich-repeat (LRR)-receptor kinase that mediates intracellular symbioses of legumes with rhizobia and arbuscular mycorrhizal fungi. It participates in signalling events that lead to epidermal calcium spiking, an early cellular response that is typically considered as central for intracellular accommodation and nodule organogenesis. Here, we describe the Lotus japonicus symRK-14 mutation that alters a conserved GDPC amino-acid sequence in the SYMRK extracellular domain. Normal infection of the epidermis by fungal or bacterial symbionts was aborted in symRK-14. Likewise, epidermal responses of symRK-14 to bacterial signalling, including calcium spiking, NIN gene expression and infection thread formation, were significantly reduced. In contrast, no major negative effects on the formation of nodule primordia and cortical infection were detected. Cumulatively, our data show that the symRK-14 mutation uncouples the epidermal and cortical symbiotic program, while indicating that the SYMRK extracellular domain participates in transduction of non-equivalent signalling events. The GDPC sequence was found to be highly conserved in LRR-receptor kinases in legumes and non-legumes, including the evolutionarily distant bryophytes. Conservation of the GDPC sequence in nearly one-fourth of LRR-receptor-like kinases in the genome of Arabidopsis thaliana suggests, however, that this sequence might also play an important non-symbiotic function in this plant.

Genetic variations in VEGF and VEGFR2 and glioblastoma outcome

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) are central components in the development and progression of glioblastoma. To investigate if genetic variation in VEGF and VEGFR2 is associated with glioblastoma prognosis, we examined blood samples from 154 glioblastoma cases collected in Sweden and Denmark between 2000 and 2004. Seventeen tagging single nucleotide polymorphisms (SNPs) in VEGF and 27 in VEGFR2 were genotyped and analysed, covering 90% of the genetic variability within the genes. In VEGF, we found no SNPs associated with survival. In VEGFR2, we found two SNPs significantly associated to survival, namely rs2071559 and rs12502008. However, these results are likely to be false positives due to multiple testing and could not be confirmed in a separate dataset. Overall, this study provides little evidence that VEGF and VEGFR2 polymorphisms are important for glioblastoma survival.

A pooled analysis of extremely low-frequency magnetic fields and childhood brain tumors

Pooled analyses may provide etiologic insight about associations between exposure and disease. In contrast to childhood leukemia, no pooled analyses of childhood brain tumors and exposure to extremely low-frequency magnetic fields (ELF-MFs) have been conducted. The authors carried out a pooled analysis based on primary data (1960-2001) from 10 studies of ELF-MF exposure and childhood brain tumors to assess whether the combined results, adjusted for potential confounding, indicated an association. The odds ratios for childhood brain tumors in ELF-MF exposure categories of 0.1-<0.2 μT, 0.2-<0.4 μT, and ≥0.4 μT were 0.95 (95% confidence interval: 0.65, 1.41), 0.70 (95% CI: 0.40, 1.22), and 1.14 (95% CI: 0.61, 2.13), respectively, in comparison with exposure of <0.1 μT. Other analyses employing alternate cutpoints, further adjustment for confounders, exclusion of particular studies, stratification by type of measurement or type of residence, and a nonparametric estimate of the exposure-response relation did not reveal consistent evidence of increased childhood brain tumor risk associated with ELF-MF exposure. These results provide little evidence for an association between ELF-MF exposure and childhood brain tumors.

Phosphorus uptake by pigeon pea and its role in cropping systems of the Indian subcontinent

Pigeon pea was shown to be more efficient at utilizing iron-bound phosphorus (Fe-P) than several other crop species. This ability is attributed to root exudates, in particular piscidic acid and its p-O-methyl derivative, which release phosphorus from Fe-P by chelating Fe(3+). Pigeon pea is normally intercropped with cereals under low-input conditions in the Indian subcontinent. Although pigeon pea can utilize the relatively insoluble Fe-P, intercropped cereals must rely on the more soluble calcium-bound phosphorus. This finding suggests that cultivation of pigeon pea increases total phosphorus availability in cropping systems with low available phosphorus.

Infectious exposure in the first years of life and risk of central nervous system tumours in children: analysis of birth order, childcare attendance and seasonality of birth

Background:

An infective, mostly viral basis has been found in different human cancers. To test the hypothesis of a possible infectious aetiology for central nervous system (CNS) tumours in children, we investigated the associations with proxy measures of exposure to infectious disease.

Methods:

In a large case–control study nested in the populations of Denmark, Norway, Sweden, and Finland of 4.4 million children, we studied the association of birth order and seasonal variation of birth with subsequent risk for CNS tumours. We identified 3983 children from the national cancer registries, and information on exposure was obtained from the high-quality national administrative health registries. We investigated the association between childcare attendance during the first 2 years of life and the risk for CNS tumours in a subset of Danish children with CNS tumours, using information from the Danish Childcare database.

Results:

We observed no association between birth order and risk of CNS tumours overall (odds ratio (OR) for second born or later born vs first born, 1.03; 95% confidence interval (CI), 0.96–1.10) or by histological subgroup, and children with CNS tumours did not show a seasonal variation of birth that was distinct from that of the background population. Childcare attendance compared with homecare showed a slightly increased OR (1.29; 95% CI, 0.90–1.86) for CNS tumours, with the highest risk observed in children attending a crèche. The strongest association was observed for embryonal CNS tumours. We found no effect of age at enrolment or duration of enrolment in childcare.

Conclusion:

These results do not support the hypothesis that the burden of exposure to infectious disease in early childhood has an important role in the aetiology of paediatric CNS tumours.

Conservation of lotus and Arabidopsis basic helix-loop-helix proteins reveals new players in root hair development

Basic helix-loop-helix (bHLH) proteins constitute a large family of transcriptional regulators in plants. Although they have been shown to play important roles in a wide variety of developmental processes, relatively few have been functionally characterized. Here, we describe the map-based cloning of the Lotus japonicus ROOTHAIRLESS1 (LjRHL1) locus. Deleterious mutations in this locus prevent root hair development, which also aborts root hair-dependent colonization of the host root by nitrogen-fixing bacteria. We show that the LjRHL1 gene encodes a presumed bHLH transcription factor that functions in a nonredundant manner to control root hair development in L. japonicus. Homology search and cross-species complementation experiments defined three members of the Arabidopsis (Arabidopsis thaliana) bHLH protein family, At2g24260, At4g30980, and At5g58010, as functionally equivalent to LjRHL1. Curiously, At2g24260 and At4g30980 mRNA species accumulate independently from the known positive regulators of root hair cell fate, while all three genes act in a partially redundant manner to regulate root hair development in Arabidopsis.

Determinants of mobile phone output power in a multinational study: implications for exposure assessment

OBJECTIVES

The output power of a mobile phone is directly related to its radiofrequency (RF) electromagnetic field strength, and may theoretically vary substantially in different networks and phone use circumstances due to power control technologies. To improve indices of RF exposure for epidemiological studies, we assessed determinants of mobile phone output power in a multinational study.

METHODS

More than 500 volunteers in 12 countries used Global System for Mobile communications software-modified phones (GSM SMPs) for approximately 1 month each. The SMPs recorded date, time, and duration of each call, and the frequency band and output power at fixed sampling intervals throughout each call. Questionnaires provided information on the typical circumstances of an individual's phone use. Linear regression models were used to analyse the influence of possible explanatory variables on the average output power and the percentage call time at maximum power for each call.

RESULTS

Measurements of over 60,000 phone calls showed that the average output power was approximately 50% of the maximum, and that output power varied by a factor of up to 2 to 3 between study centres and network operators. Maximum power was used during a considerable proportion of call time (39% on average). Output power decreased with increasing call duration, but showed little variation in relation to reported frequency of use while in a moving vehicle or inside buildings. Higher output powers for rural compared with urban use of the SMP were observed principally in Sweden where the study covered very sparsely populated areas.

CONCLUSIONS

Average power levels are substantially higher than the minimum levels theoretically achievable in GSM networks. Exposure indices could be improved by accounting for average power levels of different telecommunications systems. There appears to be little value in gathering information on circumstances of phone use other than use in very sparsely populated regions.

Head injury is not a risk factor for multiple sclerosis: a prospective cohort study

Background

The idea of physical trauma being involved in the causation of multiple sclerosis (MS) had been discussed since the earliest description of the illness. Despite the ongoing debate, the proposed association between physical and especially head trauma and MS failed to be proved or to be refuted conclusively.

Objective

To determine whether head trauma is associated with an increased risk of developing MS.

Method

A cohort of 150,868 subjects, 95,111 men, and 55,757 women registered in the National Danish Patient Registry with hospital admission for cerebral concussion, contusion, or skull fracture between 1977 and 1992, aged under 55, was selected. This trauma cohort was linked with the Danish MS Registry and followed up to the end of 1999 to retrieve subjects who had onset of MS after the year of the head trauma. We calculated the expected number of subjects, who, under a null-hypothesis, would subsequently develop MS, by using population age-, year-, and sex-specific MS-incidence densities from the Danish MS Registry.

Results

For men and women combined, the observed to expected number of MS cases (possible cases included) with onset after the head injury was 182/193.6 (standardized incidence ratio [SIR], 0.94; 95% CI, 0.81–1.09) and for possible MS excluded, 171/164.7 (SIR, 1.04; 95% CI, 0.89–1.21). In an analysis of a sub-cohort of 16,425 subjects with severe trauma (contusion, traumatic cerebral hemorrhage, and base or skull fracture), the observed to expected numbers, including possible MS, were 15/15.3 (SIR, 0.98; 95% CI, 0.55–1.62) and with possible MS excluded, 13/12.9 (SIR, 1.01; 95% CI, 0.53–1.73). As for the total group and for any of the subgroups and for men and women separately, none of the SIRs differed statistically significantly from unity. Neither were there any trends, which could be missed by type II errors.

Conclusion

Head injury of any severity does not affect the risk of acquiring MS later in life.

Seasonality of birth in children with central nervous system tumours in Denmark, 1970-2003

We investigated possible seasonal variation of births among children <20 years with a central nervous system tumour in Denmark (N=1640), comparing them with 2,582,714 children born between 1970 and 2003. No such variation was seen overall, but ependymoma showed seasonal variation.

Characterization of the interleukin-17 isoforms and receptors in lesional psoriatic skin

BACKGROUND

Th17 cells are a lineage of proinflammatory T helper cells producing interleukin (IL)-17. The importance of Th17 cells in inflammation and autoimmunity has now been recognized. The IL-17 cytokine family consists of six isoforms (IL-17A-IL-17F) whereas five members of the IL-17 receptor (IL-17R) family have been identified (IL-17RA-IL-17RE).

OBJECTIVES

To characterize the expression of the IL-17 isoforms and receptors in lesional and nonlesional psoriatic skin. Methods Keratome and punch biopsies taken from patients with psoriasis were examined by enzyme-linked immunosorbent assay and quantitative reverse transcription-polymerase chain reaction in order to measure the IL-17 isoforms and receptors.

RESULTS

We demonstrated significantly increased mRNA expression of IL-17A, IL-17C and IL-17F in psoriatic skin. In contrast, the mRNA expression of IL-17B and IL-17D was significantly decreased in lesional compared with nonlesional skin, while IL-17E mRNA was undetectable. The increased mRNA expression of IL-17A, IL-17C and IL-17F was paralleled by an increased protein accumulation of these cytokines in psoriatic skin. Analysis of the IL-17R mRNA expression revealed significantly impaired mRNA expression of IL-17RB, IL-17RC, IL-17RD and IL-17RE in lesional psoriatic skin, whereas the mRNA expression of IL-17RA was similar in lesional and nonlesional psoriatic skin.

CONCLUSIONS

This study characterizes the mRNA profile of the IL-17 isoforms and receptors in psoriatic skin lesions. Furthermore, we demonstrate for the first time augmented protein levels of IL-17A, IL-17C and IL-17F in psoriatic skin lesions, indicating a possible role for IL-17C in addition to IL-17A and IL-17F in the pathogenesis of psoriasis.

Proliferation of Cells in the Oral Mucosa, the Ear Skin and the Regional Lymph Nodes in Mice Sensitized and Elicited with a Hapten

During contact sensitivity reaction, immune cells proliferate. In order to study the histological picture of these proliferation phases, we used a mouse model of contact sensitivity in the oral mucosa and on skin. We also used bromodeoxyuridin (BrdU, an analogue to thymidin) that is incorporated into the nucleus during cell replication. The hapten oxazolone (OXA) was used to sensitize and elicit the oral mucosa and/or the ear skin. Mice were killed at various times after elicitation, and unsensitized animals were also exposed to the hapten as controls. BrdU (25 mg/kg animal) was injected i.p. 2 h before the kill. Specimens from the oral mucosa, ear skin and submandibular and auricular lymph nodes were cut and fixed in 4% paraformaldehyde. They were then treated with acid and biotinylated anti‐BrdU antibody and developed using ABC‐kit and DAB. The analyses were performed using a Leica light microscope and the computer program analysis. In the oral mucosa, the frequency of proliferating cells were increasing during the observation period, 4–24 h after elicitation, regardless of site of sensitization. The proliferating cells were found mainly in the basal cell layer of the epithelium. Similar patterns were found in ear skin. The regional lymph nodes demonstrated a few scattered proliferating cells 4 h after elicitation. After 24 h, these cells were found frequently in the whole lymph node. Control animals exhibited considerable less proliferating cells at all times. We conclude that most proliferating cells were found 24 h after elicitation locally at the hapten‐exposed sites (the oral mucosa or the ear skin) as well as in the regional lymph nodes.